Is it possible in Windows 10 build 9879 to change the default location of Onedrive? It used to be on another drive before installing the technical preview and with only 128GB on the Surface Pro I am running out of space.

Yes it is possible with Windows 10 Technical Preview build 9879 to move the OneDrive location. You must create another account on your PC, not associated with a Microsoft account. Logon to that account, then "Unlink" OneDrive (right-click the OneDrive icon in the notification icon area of the Taskbar) , move the folder and contents to the new location, then log back on with your OneDrive associated account.